[FFmpeg-user] Increasing audio

[Cecil Westerhof]

On Saturday  1 Apr 2017 22:58 CEST, Moritz Barsnick wrote:

> On Sat, Apr 01, 2017 at 22:21:04 +0200, Cecil Westerhof wrote:
>> I was asked to make videos during a ToastMasters contest. I had
>> ordered a microphone for this, but sadly it did not arrive in time.
>> So I needed to use the internal microphone from my Canon HS60 SX.
>> Being away about ten meters from the speakers, their voices are
>> much to soft. So I needed to pump up the audio. I did this with:
>
>> ffmpeg -y -i speaker.MP4 -vcodec copy -af volume=3
>> speakerAudioInc.MP4 Is that the correct way, or is there a better
>> way? When using 4 there where to much distortions.
>
> If you only want to raise the volume linearly as much as possible
> without distorting, you can analyze first:
>
> $ ffmpeg -i speaker.MP4 -vn -af volumedetect -f null -
>
> Look for the volumedetect output, especally this line:
>
> [Parsed_volumedetect_0 @ 0xbd47b80] max_volume: -7.7 dB
>
> You can use then use that value for the volume filter - note the
> "dB" syntax:
>
> $ ffmpeg -y -i speaker.MP4 -vcodec copy -af volume="7.7 dB"
> speakerAudioInc.MP4

Almost all give 0.0 dB (12), or -0.0 dB (4). When using that there
will change nothing. Or am I overlooking something?
There is also a -0.4 dB and a -0.2 dB.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof